The present invention relates to a multiplexer and particularly to a multiplexer for transferring a first large data field to a second large data field under program control.
Large grid matrix decoders or cross bar circuits are common for converting a first array of data connected to a first set of parallel conductors to a plurality of output terminals connected to a second set of parallel conductors orthogonal to the first. Permanent connections or electrically operated gates are interposed between conductors at grid crossings. Although a cross bar multiplexer circuit may be constructed in this manner, the number of component elements required is large when the arrays of conductors are large and the space requirement can become prohibitive.
As an alternative approach, a digital memory can be employed which is addressed via input leads and supplies decoded outputs from addressed memory locations. For instance if multiplexing is required between a forty-eight line input field and a twenty line output field it appears a memory depth of 2.sup.48 .times.20 (or 2.81.times.10.sup.14 .times.20) would be required to allow any combination from the forty-eight line input field to cross over to the twenty line output field. A memory of this size would be overly expensive and would require excessive time to load.